The present invention relates to a trailer comprising a trailer bed and at least one axle which extends in cross direction of the trailer and is connected to the trailer bed for suspending the wheels.
Trucking has become one of the most important modes of transportation for goods. The inherent design of a towed trailer is long in length and narrow in width, with a kingpin and fifth wheel system or a kingpin and gooseneck hitch mechanism for connecting the trailer to the towing truck. The main bearing members for loads placed on vehicles, such as for instance flatbed or semi-trailers, are a pair of main runners which are usually made of steel and run longitudinally of the vehicle. Support for a load carried by the trailer is offered by cross members mounted to the bottom side of the undercarriage. These cross members are bolted or welded perpendicularly to the webs of the main runners and define the width of the bed of the trailer. On top of the structure formed by the longitudinal and cross members, usually a floor is provided. The floor often comprises multiple floor sections which are welded to each other along their longitudinal sides or butted against each other and held in position by special guiding means and floor screws.
From WO-A-9947406 a flatbed trailer is known that unitizes the floor, the longitudinal runners and the cross runners, to provide a. lightweight, though strong trailer. However, extensive welding of the cross members and floor sections to the main runner, which extends over the whole length of the loading floor, not only reduces the load bearing strength of the complete floor structure and the loading capacity but also adds considerable weight, and therefore requires a substantial sacrifice in load capacity. Even when materials such as for instance low density aluminum are used to increase load capacity, this attempt is defeated by the extensive welding, which is time consuming and costly, and tends to minimize payload. Moreover, since the floor is built of essentially loose floor sections, they contribute very little to the load bearing function.
EP-A-967.139 discloses a semi-trailer with a wheeled lightweight chassis, which comprises a pair of spaced-apart longitudinal runners, which extend over the entire length of the trailer. At the front portion, the chassis runners are bow shaped and they extend around the ends of a forward transverse runner. The runners taper inwardly towards the rear chassis portion, to finally run parallel, three wheel axle assemblies being mounted between them in the rear chassis portion. The runners also taper inwardly towards the front portion, so that the rubbing plate assembly can be directly mounted to the runners without the need for additional reinforcement, thus saving weight. The semi-trailer disclosed in EP-A-967.139 is suitable for use with a goose-neck as well as flat construction at its front end. However, it is made of metal and does not comprise a trailer floor.